I haven’t seen "District 9" yet, but you really only need the trailer to get a heaping spoonful of the heebie jeebies. Better yet, check out Neill Blomkamp’s “Alive in Joburg,” the short film “District 9” is based on. It is, in a word, unsettling. As repulsive as the human population’s treatment of the stranded aliens is, you can almost sympathize; they are inhuman, and that otherness coupled with closeness to our homes makes the skin crawl. That much is evident in the "D9" clip below:

It’s a classic trope in sci-fi cinema, alien infiltration. Not invasion mind you, I mean aliens living among us, incognito or otherwise. Here are five classics that did it best. Before "District 9" came along, that is.

“Starman”

John Carpenter’s got a knack for directing scary alien stories. “The Thing”, with its titular extraterrestrial that can shapeshift and horrifically disfigure people, seems like an obvious first choice. “Starman” is the winner by a long shot though. The generally peaceful alien, played by a grinning Jeff Bridges, is a terrible person by human or alien standards. Not only does he take the shape of Karen Allen’s recently deceased husband, he goes ahead and sleeps with her to boot. Jerk.

“Predator 2”

The original “Predator” was suspenseful but not exactly scary. The jungle is such a forbidding environment that it feels unreal and alien on its own. Los Angeles, on the other hand, is a much more tangible place. The thought that a regular old cop and Gary Busey are the last line of defense between humanity and an alien hunter that can turn invisible is scary as hell. It’s even worse that, at the end of the picture, Danny Glover’s trophy for beating the Predator -- an 18th century pistol -- implies that these dreadlocked monsters have come to Earth and killed us as they please for centuries.

“Invasion of the Body Snatchers”

"Snatchers"' premise of aliens not only living among us but flat out replacing us is almost as old as the science fiction genre itself. The version from 1978 is the second of four different film versions of the exact same story. What makes this one so special? For starters, in addition to looking just like our dearest loved ones, these aliens make the creepiest screaming noise ever. Also, they try to kill Donald Sutherland. How can they do that?! Haven’t they seen “M*A*S*H”?! He’s such a lovable guy!

“Dark City”

This one’s candidacy is a bit questionable for this list. Is the titular city a manipulated and shattered Earth, warped beyond recognition by the Strangers? Or have these alien inhabitants brought the human captives somewhere else in space (and time?) altogether? Director Alex Proyas never explicitly states the truth in this, his greatest work. That ambiguity pervades the whole film as well as its story of a dying alien race that manipulates humanity’s memories, surroundings and very identities in an attempt to replicate the human soul. Plus, the Strangers make this really icky clicking noise.

“Batteries Not Included”

Yeah, I bet you think it’s real heartwarming. Aw, lookit the little googly-eyed UFOs! They can work as short-order cooks to help the elderly! They beat-up hired thugs! They thwart the nefarious plans of heartless industrialists! I got news for you, kids. What’s going to happen when those cute flying space monsters wake up and realize that a couple octogenarians and social misfits used them as slave labor in their second rate diner? If they can rebuild an entire building in just a few hours, then the can dismantle an entire city in mere days. Adorable? Ha. THEY WILL BE THE END OF US ALL!